1. Field of the Invention
The present invention relates to vehicle-to-roadside and vehicle-to-vehicle communication systems, communication methods, and communication control programs thereof, in particular, to a vehicle-to-roadside and vehicle-to-vehicle communication system including a vehicle-to-roadside communication and vehicle-to-vehicle communication function and a channel switching function, a communication method, and a communication control program thereof.
2. Background Art
A system of arranging a roadside communication device on the side of a road, service area and the like, and providing road information and content to the traveling vehicle is known. Normally, the system transmits and receives data with an on-board communication device within an area the radio wave from the roadside communication device can reach (see Japanese Laid-Open Patent Publication No. 2002-232948 (patent document 1)).
However, in such system, the service can be provided only when the vehicle is in the area where the radio wave from the roadside communication device reaches, and service is not provided to vehicles in traffic or waiting in line for service. Therefore, the driver in traffic or waiting in line cannot obtain the necessary information while waiting and may feel annoyance.
When desiring to provide service to all the vehicles in traffic, the roadside communication devices are required to be arranged at a constant interval on all the roads in the country, which requires an enormous cost for infrastructure building.
In order to solve such problem, an example has been disclosed. According to it, a pseudo-roadside communication device, having a communication function which is the same as a function of the roadside communication device used in the vehicle-to-roadside communication, is arranged in the vehicle, so that data transmitted from the roadside communication device is relayed through the on-board communication device and the pseudo-roadside communication device of each vehicle, and information is provided to vehicles even if they are distant from the roadside communication device (see Japanese Laid-Open Patent Publication No. 2006-166307 (patent document 2)).
Also, an example which uses the vehicle-to-vehicle communication and the vehicle-to-roadside communication simultaneously for enhancing reliability, safety, and smoothness of an automatic operation system has been proposed (see Japanese Laid-Open Patent Publication No. 10-105880 (patent document 3)).
However, in the communication system proposed in patent document 1, communication can be performed only within the range where the radio wave from the roadside communication device reaches, and thus service cannot be provided to vehicles in traffic or waiting in line for service as described above.
In the vehicle-to-vehicle communication, on the other hand, the service providing area is not limited to a specific area, but communication cannot be established unless the vehicle mounted with the on-board communication device is present nearby. Therefore, it is desired that the service providing area by the vehicle-to-roadside communication and the vehicle-to-vehicle communication are complemented with each other to enhance safety and convenience.
By the way, in the example of patent document 2 aiming to complement the deficiencies caused by performing the vehicle-to-roadside communication and the vehicle-to-vehicle communication, the cost for the roadside communication device infrastructure building can be reduced, but on the other hand cost increases as the on-board communication device for the vehicle-to-roadside communication and the pseudo-roadside communication device similar to the roadside communication device for the vehicle-to-vehicle communication is required to be arranged as the on-board communication device, whereby cost can not be reduced in the system as a whole. This example is formed on the premise that the vehicle users bear a burden, so the problems still remain.
Patent document 3 discloses a system specialized for automated driving, and has an aspect different from the information communication system in that its main aim is to detect the position of the roadside communication device and the other vehicles. And, similar to the example of patent document 2, patent document 3 has a drawback in that two communication equipments, for the vehicle-to-vehicle communication and the vehicle-to-roadside communication, are required to be mounted.